As is known in this technical field, various attempts have been made to use minimally invasive surgery for spine operations. In this respect, so-called PLIF (Posterior Lateral Interbody Fusion) operation techniques have been developed. According to such an operation technique, the intervertebral disc is removed through a posterior access and an intervertebral space is filled with autologous bone.
Further developments of this PLIF technique resulted in the application of a so-called TLIF operation technique based on a transforaminal access. This technique provides for the dorsal transforaminal introduction of titanium cups (so-called cages), which are filled with autologous bone. At the same time, dorsal instrumentation and stabilization are applied.
The advantage of the briefly outlined method is that no transabdominal or retroperitoneal additional access has to be used. A known prior art approach is described in the U.S. Pat. No. 6,923,814, which discloses a system for performing spinal fusion between adjacent cervical vertebrae, including an implant and an introduction system. The introduction system comprises a fork member and a general tubular lock member. A thread feature at the end of the instruments transfers a rotational movement into a linear movement. The linear movement causes the deformation of the fork member and therefore engagement of the instrument with the implant. The implant instrument locking is done by a thread member that, however, does not simplify the working steps compared to a simple thread. In case of a 90° locking, less manipulation steps may be required, but the instrument does not allow angularly adjustment of the implant with respect to the instrument.
Another approach is disclosed in the U.S. Pat. No. 6,159,215, disclosing a method for delivering a vertebral body spacer to the disc space. The instrument has two fingers, which are movable relative to one another and adapted to grip the spacer when the shaft is moved to actuate the fingers. The handle portion includes a grip and a trigger for the grip, causing the fingers to move toward one another. The implant is not, in-situ, angularly adjustable. The fixation is done by way of a linear movement.
Another approach is described in the U.S. Patent Application Publication No. 2006/0235426, which discloses an implant, and an instrument and method for positioning a spinal implant in a spinal disc space between adjacent vertebrae. That implant is fixed by a hinged forceps tip. The forceps tip can be angularly adjusted with respect to the implant and the instrument is permanently connected to the implant. This approach has a complex instrument locking mechanism instead of a 90° lock/unlock mechanism and it's impossible to engage the instrument in-situ.
Another approach is disclosed in the U.S. Pat. No. 66,174, which discloses an implant insertion device with a gripping device on one end. The jaws are movable between the gripping position to grasp the implant between the gripping elements and releasing position to release the implant. A hollow sleeve is slidably disposed over the jaws for forcing the jaws together towards the gripping position. The implant fixation is done with a linear movement of the sleeve, but this linear movement can cause tissue damage and it is not as simple as a 90° locking.
Another approach is disclosed in U.S. Patent Application Publication No. 2004/0153065. The approach includes an intervertebral implant. The instrument is connected to the implant by a hinge element. The rotation of the axial sleeve of the instrument case an axial movement of the shaft. This movement is pivoting the spacer. It is impossible to engage the instrument is-situ. Angulation is mainly possible in only one direction. The engagement/disengagement mechanism may be inferior compared to a 90° locking mechanism because of its complexity.
U.S. Patent Application Publication No. 2005/0096745 discloses an implant for the transforaminal intercorporal fusion of lumbar vertebral column segments. The attachment part to the instrument is configured as a slot. Within this slot, the instrument can be engaged. The instrument can be fixed in different angles with respect to the implant. The interface is a friction lock, which has reduced stability compared to a positive lock. The fixation is done by a thread mechanism. The engagement/disengagement mechanism may be less desirable as compared to a 90° locking mechanism because of the required working steps.
Another approach is disclosed in the European Patent No. EP1841385B1. This approach includes an implant for the transforaminal intercorporal fusion of lumbar vertebral column segments. The attachment part to the instrument is configured as a revolute joint. Within the revolute joint, there is a thread as an interface to the instrument. The instrument can be fixed in different angles in respect to the implant. The interface is a friction lock, which has reduced stability as compared to a positive lock. In addition, in-situ engagement is not possible due to the thread. The fixation of the implant to the instrument is more difficult compared to a 90° locking instrument.